Development of new surface treatments for the adhesive bonding of aluminum surfaces

Abstract

Bi-functional water-soluble polymers have been investigated as bonding layers (BL) on aluminum surfaces to promote the adhesion of adhesives for structural bonding applications in the automotive sector. The BLs are located at the interface between two parts: the aluminum substrate and the adhesive (an epoxy-dicyandiamide). The formation and the morphology are studied mainly by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Many process parameters have been investigated such as: i) long or short immersion time in the treatment baths containing the polymers, ii) formulation using three different concentrations. The performances of the BLs under these different operating conditions are evaluated via several mechanical tests: micro-scratch, three-point bending, single lap shear. Results were compared with results obtained with already existing products, launched for the same application, surface treatment prior to structural adhesive bonding of aluminum in transportation.